The use of a harrow disk blade in harrow equipment for preparing agricultural land for seeding after plowing is well-known. Indeed, the pulverizing element utilized by a harrow for pulverizing and smothering the soil may be an agricultural tool with spikes, spring teeth and/or disk blades. However, when disk blades were used as the cultivating instrument, it was found that the metal blade had a short wear life without a protective coating of a material to reduce abrasion of the metal surface. Accordingly, methods were devised to apply a hard-faced matrix composition to the surface of the harrow metal blade to protect the metal blade against abrasion and wear.
As a harrow metal blade designed for efficient use, the harrow metal blade has a convex side and a concave side on the opposite side. As the harrow metal disk blade moves through the soil, forces, which can be unequal, are applied to the convex and concave surfaces of the harrow disk blade. Soil type, soil consistency, manner and method of machine cultivation, and soil composition can affect the degree of abrasive forces applied to the harrow metal disk blade. Typically, a hard-faced coating was applied to the convex side of the harrow metal disk blade based on soil abrasion on the convex side of the metal blade to protect the blade against abrasion and wear.
With increased use of highly abrasive soils and increased cultivation of growing areas as in California and Arizona where extensive cultivation is required to prepare a seedbed for planting, it has been found that application of a protective hard-facing coating to the convex side of the harrow metal disk blade was insufficient to protect the concave side of the harrow metal disk blade from excessive wear. Excessive soil forces on the concave unprotected side of the disk blade cause wear of the unprotected steel on the concave side of the harrow metal disk blade. The harrow metal disk blade accordingly wears from its original size to the point where the metal of the harrow disk blade on the concave side is worn sufficiently to cause the protective band of hard-facing coating material on the opposite convex side to chip and to break off.
It is therefore an object of the present invention to provide a method for applying a protective sintered hard-faced composition of carbide refractory materials resistant to surface abrasion and surface wear to the harrow metal disk blade on both the concave and convex sides of the harrow metal disk blade to provide a coated harrow tempered metal disk blade with increased protection against abrasion and wear from highly abrasive soils and from increased cultivation use on both sides of the harrow metal disk.
It is a further object of this invention to provide a double-coated sintered hard-faced harrow tempered metal disk blade for application as a farm implement harrow blade wherein the double-coated sintered hard-faced disk blade has increased resistance to wear and abrasion in highly abrasive soils and use in areas of extensive cultivation wherein the tempered metal blade has increased strength and resiliency from the tempering process.
In its prior art, hard-facing matrix compositions and methods of applying hard-facing to metal articles are taught.
U.S. Pat. No. 3,406,028 to Woock, teaches and claims a hard-facing matrix composition and the method of preparing the composition, which bonds to metals to be protected against abrasion and wear. The matrix comprises carbides such as tungsten carbide, boron carbide, molybdenum carbide, and titanium carbide, the greater percentage of carbides, the greater the wear resistance of the matrix.
U.S. Pat. No. 3,056, 693 to Woock teaches and claims a method of hard-facing a metallic article whereby articles can be hard-faced with an abrasion resistant refractory coating fused to the base metal and by which a wide range of coating thicknesses can be utilized. The patent teaches that the service life of metallic articles can be increased by a factor of several times if the surfaces subject to war can be treated with a coating of hard-facing of refractory material highly resistant to abrasion.
U.S. Pat. No. 3,056,383 to Woock teaches and claims an apparatus for coating metal articles with a layer of hard-facing material. The invented apparatus provides a means for applying a band of the coating mixture to the article along a peripheral portion thereof with one lateral side of the band extending along one surface of the article and the other lateral side of the band extending along the adjacent edge of the article. The invented apparatus also provides means for controlling the thickness of the coating layer on the article undergoing coating.
U.S. Pat. No. 6,206,116 to Saxman teaches a drill bit having a cutter cone assembly defined by a base portion, a nose, a conical surface extending from the base portion formed with a with a first and second row of cutting elements circumferentially arranged. The cutting structure is machined by a series of plunge cuts or lathe turns. For one embodiment, the crest of each cutting element has a general configuration of an ogee curve. A layer of hard facing material is taught but not claimed. The material may be applied to selected areas of the machined cutting structure.
U.S. Pat. No. 5,129,437 to Nettles, et al. for a wood chipper teaches and claims a plurality of segmental knife holders supporting a removable knife blade assembly. The log-facing surface of the knife holder is helicoid rather than flat. The knife holders each have a base plate which removably mounts onto said disk and a wear plate replaceably affixed by welding onto a proximal face of the base plate and having a helicoid proximal surface rather than flat surface. A hard facing of a predetermined thickness is formed on its proximal surface with a thickness of 0.20 to 0.050 inches. The hard facing is formed by a thermal spray treatment with powdered tungsten carbide.
U.S. Pat. No. 5,456,323 to Hill teaches and claims an agricultural sweep for cutting through the ground to till the ground. The sweep has a wear resistant cutting surface for rendering the stem of the sweep resistant to abrasion. The wear resistant surface is composed of an alloy compound.
Japanese Publication JP 5501 4960A to Mesato teaches a blade coating by metal spraying to increase the durability of the blade. At least every alternate layer coating is sprayed with Ni—Cr—B—Si alloy. A tungsten-carbon compound is sprayed on the front of the revolving blade and the back face of the rear edge. The concave surface is coated with the same material.
U.S. Pat. RE27,851 to Alessi teaches and claims a hard facing composition for application to a metal base to resist abrasion comprising a powdered alloy having a composition by weight of 1% to 3% carbon; 13% to 17% chromium; 3% to 7% nickel; 2.25% to 7% silica; 0.2% to 0.5% manganese; 2% to 4% borin, and 65% to 75% iron; about 3% of a potassium borate flux; up to about 15% by weight of water as a liquid vehicle; and about 1% bentonite clay as a suspension agent.